TEM INVESTIGATIONS IN THE PFN PFW PZN PEROVSKITE SYSTEM

Using an analytical electron microscope, the distribution of phases and order-disorder phenomena in the Pb(Fe1/2Nb1/2)O3-Pb(Fe2/3W1/3)O3 Pb(Zn1/3Nb2/3)03(PFN-PFW-PZN) perovskite system were examined. It was found that after sintering the solid solution, small cubic pyrochlore particles with chemical composition close to Pb(Fe0.28Zn0.01 Nb0.50W0.21)O3.4 and a(o) = 1.05 nm were present in the 0.8 mol % Pb2WO5-0.2 mol % PbO liquid phase. In samples fired at 1000-degrees-C, several 1 0 nm sized ordered areas with faint F spots in the selected-area electron diffraction pattern and (h + 1/2 k + 1/2 I + 1/2) lattice fringes were found. Similar features were found in the PZN perovskite monocrystal, leading to the conclusion that local 1:1 ordering of cations (presumably Zn2+ and Nb5+) in the PFN- PFW PZN system caused partial decomposition of the perovskite phase at firing temperatures equal to or higher than 850-degrees-C.